This application claims foreign priority to German Patent Application 10 2009 020 703.1, filed May 11, 2009, which is hereby incorporated by reference herein.
The invention relates to an active carbon filter intended for the fuel supply system of the internal combustion engine of a vehicle and consists of a housing with ports for connection with the top space of a tank, for connection with the ambient atmosphere, and for connection with an intake manifold of the internal combustion engine, wherein the inside of the housing accommodates flow paths for the different operating states of the active carbon filter between these ports, and wherein at least one chamber containing a filler comprised of active carbon is arranged along the progression of these flow paths.
When using a hybrid drive characterized by an internal combustion engine and an electric engine for a motor vehicle, the time for which the internal combustion engine is in operation is reduced by the time for which the electric engine is in operation. Among other things, this fact is also important for an active carbon filter connected with a fuel tank that supplies the internal combustion engine, since its regeneration is limited to the times for which the internal combustion engine is in operation.
The fuel tank is usually in contact with the ambient atmosphere by way of a line, which prevents both a pressure buildup and a partial vacuum in the top space of the tank, which can arise during refueling, the removal of fuel, or an evaporation of fuel due to temperature conditions. An active carbon filter conventionally placed in this line is intended to prevent hydrocarbons from being uncontrollably released into the environment in this way.
Such an active carbon filter globally consists of an apparatus designed to accommodate active carbon particles, with ports for establishing a connection with the fuel tank, ambient atmosphere, and intake manifold of the internal combustion engine.
In order to reduce the amount of active carbon to be used, the port connected with the mentioned intake manifold routes ambient air through the active carbon filling of the filter during the scavenging phase, which takes up hydrocarbons adsorptively bound through desorption and introduces the latter into the combustion chamber of the engine, so that the active carbon is regenerated as a result. However, this process presupposes that the internal combustion is in operation. Since the amount of hydrocarbons exiting the top space due to evaporation and to be absorbed in the active carbon filling is independent of the operating time of the vehicle, the regeneration process must be concluded in a shorter time in a hybrid drive.
It is generally known that the conditions for regeneration in terms of acceleration can be improved via the thermal conditions of this conversion by heating the air used for regeneration and/or the active carbon.
Known from Document DE 102 95 967 T5 is an active carbon filter of this type in which the active carbon filling can be heated. In this case, use is made of plate-shaped or tubular, electrically operated heating elements with PTC characteristics that project into the active carbon filling from below, thereby setting up a temperature limit in an easy manner.
Known from Document US 2006/0174857 A1 is an apparatus for heating the air intended for regenerating an active carbon filter, which consists of component that is equipped with several channels running parallel to each other and carrying the air to be heated and made out of an active, heat-insulating material, wherein the air is heated by electrical resistor elements that extend inside the channels in their longitudinal direction.
Within the framework of the specific structural configuration, these known techniques for pre-warming the air used to regenerate the active carbon filling of such a filter under certain conditions have only a limited suitability for setting up a regeneration process that is sufficiently quick even for a hybrid drive, given the inadequate heat transfer.
Known at the company of the applicant for heating the air for regeneration purposes is to use an electrical conductor made of carbon, around which the air to be heated streams. Comparable hereto is a monolithic molding made of an active material that absorbs hydrocarbons, which is provided with boreholes extending in its longitudinal direction, and is simultaneously used as an electrical conductor to heat the air streaming through it.
The problem with regard to the two aforementioned technical solutions is the requirement for an exact and especially reliable temperature controller, since it is necessary that the ignition temperature of the hydrocarbons not be reached, and in particular that any sparking be prevented.